/*
* Copyright (c) 1988, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* This defines a structure for a ring buffer.
*
* The circular buffer has two parts:
*(((
* full: [consume, supply)
* empty: [supply, consume)
*]]]
*
*/
/*
* The following is a clock, used to determine full, empty, etc.
*
* There is some trickiness here. Since the ring buffers are initialized
* to ZERO on allocation, we need to make sure, when interpreting the
* clock, that when the times are EQUAL, then the buffer is FULL.
*/
static u_long ring_clock = 0;
/* Number of bytes that may be supplied */
int
ring_empty_count(Ring *ring)
{
if (ring_empty(ring)) { /* if empty */
return ring->size;
} else {
return ring_subtract(ring, ring->consume, ring->supply);
}
}
/* number of CONSECUTIVE bytes that may be supplied */
int
ring_empty_consecutive(Ring *ring)
{
if ((ring->consume < ring->supply) || ring_empty(ring)) {
/*
* if consume is "below" supply, or empty, then
* return distance to the top
*/
return ring_subtract(ring, ring->top, ring->supply);
} else {
/*
* else, return what we may.
*/
return ring_subtract(ring, ring->consume, ring->supply);
}
}
/* Return the number of bytes that are available for consuming
* (but don't give more than enough to get to cross over set mark)
*/
int
ring_full_count(Ring *ring)
{
if ((ring->mark == 0) || (ring->mark == ring->consume)) {
if (ring_full(ring)) {
return ring->size; /* nothing consumed, but full */
} else {
return ring_subtract(ring, ring->supply, ring->consume);
}
} else {
return ring_subtract(ring, ring->mark, ring->consume);
}
}
/*
* Return the number of CONSECUTIVE bytes available for consuming.
* However, don't return more than enough to cross over set mark.
*/
int
ring_full_consecutive(Ring *ring)
{
if ((ring->mark == 0) || (ring->mark == ring->consume)) {
if ((ring->supply < ring->consume) || ring_full(ring)) {
return ring_subtract(ring, ring->top, ring->consume);
} else {
return ring_subtract(ring, ring->supply, ring->consume);
}
} else {
if (ring->mark < ring->consume) {
return ring_subtract(ring, ring->top, ring->consume);
} else { /* Else, distance to mark */
return ring_subtract(ring, ring->mark, ring->consume);
}
}
}
/*
* Move data into the "supply" portion of the ring buffer.
*/
void
ring_supply_data(Ring *ring, unsigned char *buffer, int count)
{
int i;
while (count) {
i = MIN(count, ring_empty_consecutive(ring));
memmove(ring->supply, buffer, i);
ring_supplied(ring, i);
count -= i;
buffer += i;
}
}
